Cooking food is one of the oldest human activities still practiced today. Cooking has evolved from simply heating over a fire to using various types of containers (cooking pots, frying pans, baking tins, crock pots, double boilers, etc.) in convection ovens which are heated by electricity or gas. A number of different types of materials having high temperature resistance have been used for these containers, the most common presently being metal. People have become used to cooking in metal containers, both for the methods of cooking used and the taste and texture of the foods produced.
In the last 20 years or so, as thermoplastic polymers (TPs) having better high temperature resistance have been developed, the use of these polymers for ovenware has been proposed, see for instance U.S. Pat. Nos. 4,626,557, 4,503,168, 4,585,823, 5,308,913, and 5,141,985, and European Patent Application 846,419, all of which are hereby included by reference. These polymeric cooking containers can be used in thermal ovens and often can withstand the highest temperatures usually used in these ovens, for example about 290° C. (˜550° F.) or more. These containers have the advantage of being molded into practically any shape, may be containers that are easily sealed so the contents can be refrigerated or frozen, and are relatively low in weight. However when cooking food in these containers the cooking method (time and/or temperature for example) may have to be varied from the method used for a metal container, and/or the food may not have the same taste and/or texture. For example bread or a casserole baked in a plastic container may not be browned on the outside surface which is in contact with the cooking container surface as it is in a metal container. This is primarily due to the fact that polymers in general tend to have very low thermal conductivities, especially when compared to metals. Thus a TP cooking container which behaved more like a metal container would be desirable.